The present invention relates to cable locating systems for buried utility company cables and, more particularly, to a system using spare communication lines in the conveyance to communicate with and control cable locating units at remote, inaccessible locations.
Most utilities, such as those that provide electric, water, gas and telephone service, bury their conveyances (i.e., pipes and cables) undergroundxe2x80x94both for reasons of safety and esthetics. Underground burial also protects such conveyances from direct exposure to the elements. Once a utility buries a conveyance, the utility marks the location on a map (using, for example, a physical landmark such as a building, road, or bridge) to facilitate location of the conveyance in the event of a disruption of service along the line. Using a physical landmark as a point of reference incurs the disadvantage that such landmarks can, and do, undergo change. For example, a building may undergo renovation or even demolition whereas a road may be widened, thus altering the previously-existing physical relationship between the landmark and the buried conveyance. Consequently, relying on the physical relationship between a landmark and the conveyance may not always yield an accurate indication of the location of the conveyance.
To facilitate greater precision in the location of their conveyances, utilities often use electromagnetic detection techniques. One such locating technique is disclosed in U.S. Pat. No. 5,644,237, issued to H. Eslambolchi et al. on Jul. 1, 1997. Eslambolchi et al. describe and claim a locating technique, whereby a first transmitter impresses a first locating tone on a conveyance to allow a technician to generally locate the conveyance using a signal-locating receiver. Additionally, a second transmitter may be used to provide a coded, near-DC signal on the conveyance to allow the technician, using a second receiver, to precisely locate the conveyance of interest.
Service providers, such as ATandT, often utilize a large number of transmitters for providing cable-locating tones on their buried conveyances. Often, the transmitters are located at remote, unmanned facilities, requiring that a technician travel to such a facility to service the cable-locating transmitter. Such servicing may include, for example, upgrading the software used in the transmitter, turning xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d the transmitter, changing the specific cable-locating frequency used for that conveyance, etc. One prior art technique to improve the efficiency of controlling a group of remote cable-locating transmitters is disclosed in U.S. Pat. No. 6, 240,373 issued to P.J. Boggs et al. on May 29, 2001. In the Boggs et al. arrangement, a centrally-disposed control unit includes a database and communication lines linked to each of the remote transmitters. Simultaneous software upgrades to a group of remote cable-locating transmitters can then be simply controlled from the central location, with the upgrades transmitted over a dedicated telephone line to each remote facility.
In some remote areas, however, there are no telephone lines available to provide for an interconnection between a cable-locating transmitter and a central controller. In these instances, therefore, it is necessary to have a technician travel to the remote location and manually operate the system to perform the necessary software upgrade or perform modification(s) in tone frequency, power, xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d status, and the like. In today""s environment where productivity must be increased, a new system is needed to control the cable-locating transmitters at locations without telephone service.
The need remaining in the prior art is addressed by the present invention, which relates to cable locating systems for buried utility company cables and, more particularly, to a system using spare communication lines in the actual conveyance to communicate with and control cable locating units at remote, inaccessible locations.
In accordance with the present invention, a first cable-locating transmitter unit with access to a telephone line is used as a xe2x80x9ccontrol unitxe2x80x9d to pass control signals along to other cable-locating transmitters without telephone access. A spare communication line (for example, a pair of spare fibers in a fiber optic cable conveyance) in the control unit is coupled to a conventional device used to control the operation of a cable-locating transmitter. This spare line is then subsequently coupled to a remotely-disposed cable-locating transmitter, which in turn couples the spare line to another remotely-disposed cable-locating transmitter, and so on, until a group of transmitters are coupled to a telephone-connected control unit through the spare communication line. In the case of a fiber optic cable conveyance where the spare line is a pair of optical fibers, additional opto-to-electronic conversion apparatus is required at each remotely-disposed cable-locating transmitter.
In operation, therefore, control messages may be sent (using DTMF tone sequences, for example) over the telephone line to the xe2x80x9ccontrolxe2x80x9d cable-locating transmitter. The control signals will include the particular address of the cable-locating transmitter that needs to be modified. Each transmitter will, in turn, receive the message, and if the address is for that particular transmitter, will proceed to perform the necessary modifications. If the address does not match the current transmitter, the message will be sent on down the line to the next transmitter, where the process will be repeated until the desired cable-locating transmitter is reached and the modification performed.
In a preferred embodiment of the present invention, a return signal path is used to carry a confirmation signal to allow the technician to know that the command has reached the proper unit and the modification has been performed.
Other and further embodiments and aspects of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings.